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aA'cl i '141 Z25 January 1999 Y i CID AGE-NC Project No 97-0301 Page 2 of 6 mg/kg(milligrams per kilogram) Volatile aromatics (benzene, toluene, ethylbenzene and xylenes BTEX) were detected at concentrations up to 520 mg/kg, methyl tertiary butyl ether (MTBE) was detected in two stockpiled soil samples at concentrations up to 0 012 mg/kg i i 23 REGIONAL GEOLOGIC SETTING The property is situated within the Great Valley Geomorphic Province of California, a large, elongate, northwest trending, asymmetric structural trough The Great Valley Province has been filled with thick sequences of sediment ranging in age from Jurassic to Recent, creating a nearly flat- lying alluvial plain,extending from the Tehachapi Mountains in the south to the Klamath Mountains in the north The western and eastern boundaries of this province are comprised of the California Coast Range and the Sierra Nevada, respectively Rocks composing the basement complex of the province have not been completely defined but are believed to be metamorphic and Igneous in origin The northern and southern portions of the Great Valley Province have been designated the Sacramento and San Joaquin Valleys, respectively Based on the General Soil Map from the San Joaquin County Soil Survey,published by the United States Department of Agriculture Soil Conservation Service in 1992, the site area is within the Jackson-Hallenbeck-Stockton (JHS) association The JHS soils are located within basins, and generally consist of moderate to poorly drained fine textured soils The soils are generally derived from both marine and non-manne sediment, and are generally formed in alluvium derived from mixed rock sources The Modesto, Riverbank, Turlock Lake Formations and overlying recent alluvium are the principal source of domestic ground water in the 13,500 square-mile San Joaquin Valley Ground Water Basin (Basin 5-22) This basin is drained primarily by the San Joaquin River The nearest surface water -----feature in the-vicinity of the property is the-Walker-Slough, approximately 2,000 feet northeast of the property 2 4 GROUND WATER DEPTH AND FLOW DIRECTION Based on review of the Lines of Equal Depth to Groundwater Spring 1996 map published by the San Joaquin County Flood Control District and Water Conservation District(FCD&WCD),the estimated depth to ground water at the site is between 30 and 40 feet below surface grade(bsg) Review of the map Lines of Equal Elevation of Groundwater Spring 1996 (FCD&WCD) depicts the regional ground water flow direction towards the northeast Review of historical depth to ground water maps (FCD&WCD) dating back to 1971 suggests that Advanced GeoEnwronmenta1,Inc